3rd Generation Partnership Project Long Term Evolution (3GPP LTE) and LTE-Advanced (LTE-A) communication systems are briefly described below as exemplary mobile communication systems to which the present invention can be applied.
FIG. 1 schematically illustrates a network structure of an Evolved-Universal Mobile Telecommunications System (E-UMTS) as an exemplary mobile communication system. The E-UMTS is an evolved form of a conventional UMTS and standardization thereof is ongoing in the 3GPP. The E-UMTS may be considered a Long Term Evolution (LTE) system. For detailed contents of the technical specifications of the UMTS and the E-UMTS, reference may be made to Release 7 and Release 8 of “3rd Generation Partnership Project; Technical Specification Group Radio Access Network”, respectively.
As shown in FIG. 1, the E-UMTS may include a User Equipment (UE), a base station (hereinafter, referred to as an “eNode B” or “eNB”), and an Access Gateway (AG) positioned at the end of the network (E-UTRAN) and connected to an external network. Generally, the eNode B may simultaneously transmit multiple data streams for broadcast services, multicast services and/or unicast services.
One or more cells may exist in one eNode B. Each cell is set to provide one of bandwidths of 1.25, 2.5, 5, 10, 15, and 20 MHz and provides a downlink or uplink transmission service to a plurality of UEs. Different cells may be set to provide different bandwidths. The eNode B controls data transmission and reception of multiple UEs. The eNode B transmits downlink (DL) scheduling information for DL data to inform the UE of a time/frequency region in which the DL data will be transmitted to the UE, information regarding encoding, data size, Hybrid Automatic Repeat and reQuest (HARQ) related information, and the like. In response to uplink (UL) data, the eNode B transmits UL scheduling information to the UE to inform the UE of a time/frequency region which can be used by the UE, information regarding encoding, data size, HARQ related information, and the like. An interface may be provided between eNode Bs for transmission of user traffic or control traffic. A Core Network (CN) may include the AG and a network node for user registration of the UE. The AG manages the mobility of the UE in units of Tracking Areas (TAs), each including a plurality of cells.
Although radio access technology has been developed to LTE based on Wideband Code Division Multiple Access (WCDMA), the demands and expectations of users and providers continue to increase. In addition, since other radio access technologies continue to be developed, evolution to new technologies is required to secure high competitiveness in the future. Decrease in cost per bit, increase in service availability, flexible use of a frequency band, simple structure, open interface, suitable UE power consumption and the like are required.
Recently, standardization of a successor technology to LTE is underway in 3GPP. In this specification, this technology is referred to as “LTE-A”. Main differences between the LTE system and the LTE-A system include system bandwidth and introduction of a relay.
The LTE-A system aims to support a wideband of up to 100 MHz. To accomplish this, the LTE-A system adopts carrier aggregation or bandwidth aggregation technology which uses a plurality of frequency blocks to achieve wideband.
Carrier aggregation (or carrier integration) uses a plurality of frequency blocks as a single large logical frequency band in order to use a wider frequency band. The bandwidth of each frequency block may be defined based on the bandwidth of a system block used in the LTE system. Each frequency block is transmitted using a component carrier.
Although the LTE-A system, which is a next-generation communication system, adopts the carrier aggregation technology, conventional technologies cannot support uplink power control operations of a UE in a multi-carrier system. However, no specific studies have been conducted in this regard.